LACONIA — The city may soon find itself saddled with the cost of addressing lingering contamination from a burn dump that operated on Frank Bean Road and Morin Road for some three decades between the 1920s and the 1950s.

The area in question is off Rte. 107, near the Laconia Ice Arena.

A third report on the site, prepared for the city at the request of the New Hampshire Departmental of Environmental Services (DES) by Sovereign Consulting, Inc. of Concord concluded that "a plan for mitigation of future risk at these properties is warranted."

The burn dump is part of a site that sprawls over some 75 acres on either side of Frank Bean Road, most in the city and some in Gilford. which also includes an abandoned landfill. The burn dump itself extends over four lots — two residential and two commercial — totaling about 3.5 acres. Three of the lots abut one another on the west side of Frank Bean Road and the fourth is bordered by Frank Bean Road to the west and Morin Road to the east.

The property was owned by Leon Morin, who either leased it the city as a disposal site or accepted refuse from the city for incineration.

The site first drew the attention of DES in May, 2003 when David Farley, doing business as Dolphin Point, LLC, a marine contractor, complained of encountering buried refuse and foul odors while excavating for a foundation on his lot on Frank Bean Road. The lot is flanked to the south by a property leased to CBH Landscape Contractors and to the north by a residential parcel.

In 2008, Weston Solutions, Inc. found levels of six metals as well as volatile organic compounds (VOCs) and polycyclic aromatics hydrocarbons (PAHs), which are byproducts of burnt fuels, in samples collected across the 75 acres, including the burn dump. Levels were sufficiently elevated to warrant further investigation.

Three years later Terracon Consultants, Inc. reported that a thin layer of clean fill covered the site and concluded that surface soils were unlikely to pose a significant risk to human health. However, DES replied that a risk assessment of surface soils would not diminish the requirement for mitigation, suggesting resources would be better applied to remedial measures, and requested further investigation.

Sovereign sunk 11 monitoring wells and 20 soil borings to determine the extent and nature of materials at the burn dump. The report estimates the dump stretches along Frank Bean Road for about 1,000 feet and is 250 feet wide at its widest point. Likewise, the dump is between 15 feet and 20 deep, though some refuse was found at a depth of 32 feet. Assuming dimensions of 1,000 feet by 200 feet by 15 feet, the report estimates the contains approximately 110,000 cubic yards of "burn dump material."

Like the earlier investigations, Sovereign also found metals and PAHs in excessive concentrations, In addition, chlorinated VOCs were detected on three of the four lots, trichloroethylene on one lot and petroleum residues on another. But, the report noted "significant adverse impact to native soils has not been documented." Nor did samples of private wells serving the four lots indicate adverse impacts to the quality of drinking water.

Sovereign suggested that a mitigation plan could include some combination of removing and covering the burn dump materials along with changing or restricting the use of the site. The report noted that each of the four parcels will be evaluated separately and specific measures to address the risk of exposure to harmful materials applied to each. Meanwhile, the report recommends further sampling of drinking water and groundwater and additional borings to define the southern extent of burn dump materials.

DES has yet to respond to the report and its recommendations. City Manager Scott Myers said that he will update the City Council on the next steps in addressing the situation when it meets on Monday.